Pliable air duct with pressure responsive discharge outlets

ABSTRACT

An air-handling system (preferably a variable air volume system) includes an inflatable air duct with a discharge member whose discharge opening varies with the static pressure or flow rate within the duct. To prevent the duct from deflating at low airflow rates, the discharge opening, in some embodiments, tends to close in response to reduced air pressure associated with the lower airflow. The closing of the discharge opening prevents the static pressure from decreasing as much as the pressure would otherwise if the discharge opening were fixed. In some embodiments, the discharge opening responds to static pressure or airflow within the duct such that the discharge member redirects the discharge air as a function of the static pressure of flow volume. Warmer air at relatively low volume, for instance, can be directed downward, and cooler air at greater airflow rates can be directed upward.

FIELD OF THE DISCLOSURE

The subject invention generally pertains to air ducts and more specifically to a discharge outlet for such a duct.

BACKGROUND

To help control the temperature, humidity, or ventilation of a building, variable air volume, or VAV systems, supply air at a flow rate that varies to meet the building's heating, ventilating, or air conditioning demand. In some cases, the total flow rate is varied by adjusting the speed of a variable speed blower, which forces the air through a network of supply air ducts that run through the building. The supply air ducts usually include a number of variable opening valves for apportioning the air as needed.

Although VAV systems often use relatively rigid sheet metal ductwork, pliable fabric ducts can also be used. A DUCTSOX duct by the DuctSox Corporation of Milwaukee, Wis., for example, includes a flexible fabric wall that inflates to a generally cylindrical shape by the air pressure within the duct. Fixed or manually adjustable discharge openings in the wall of the fabric duct release the air to desired areas of the building. A few examples of fabric air ducts are disclosed in U.S. Pat. Nos. 5,655,963; 6,280,320; and 6,425,417, which are specifically incorporated by reference herein.

A problem unique to VAV systems with fabric air ducts as opposed to rigid ones is that at lower airflow rates, fabric ducts tend to partially deflate. A partially deflated duct can create a poor appearance or may interfere with whatever might be directly beneath the duct. Consequently, a need exists for maintaining the shape of a fabric air duct over a range of airflow conditions.

SUMMARY OF THE INVENTION

In some embodiments, a fabric air duct includes a variable discharge opening whose degree of opening varies with the air pressure within the duct.

In some embodiments, a fabric air duct includes a plurality of such variable discharge opening distributed along the length of the duct.

In some embodiments, a fabric air duct includes a variable discharge opening that includes a resiliently flexible flap for providing a degree of opening that varies with the air pressure or flow rate within the duct.

In some embodiments, the resiliently flexible flap is an integral extension of the duct's fabric sidewall.

In some embodiments, a fabric air duct includes a variable discharge opening whose degree of opening increases with an increase in air pressure or increase in flow rate within the duct.

In some embodiments, the variable discharge opening is disposed along a sidewall of the duct.

In some embodiments, a variable speed blower delivers air to a fabric air duct at a variable flow rate.

In some embodiments, a fabric air duct includes a variable discharge opening that redirects the flow of air in response to the air pressure or flow rate within the duct.

In some embodiments, a fabric air duct includes a variable discharge opening that redirects the flow of air in a more upward direction in response to an increase of air pressure or flow rate within the duct.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an air-handling system that includes an inflatable duct with a plurality of discharge members whose degree of opening varies with the air pressure and flow rate within the duct.

FIG. 2 is a side view of a discharge member subjected to reduced airflow and relatively low static pressure.

FIG. 3 is a cross-sectional view taken along line 3-3 of FIG. 2.

FIG. 4 is a side view of the discharge member of FIG. 2 but with the member subjected to increased airflow and relatively high static pressure.

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 4.

FIG. 6 is a side view of another discharge member subjected to reduced airflow and relatively low static pressure.

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 6.

FIG. 8 is a side view of the discharge member of FIG. 6 but with the member subjected to increased airflow and relatively high static pressure.

FIG. 9 is a cross-sectional view taken along line 9-9 of FIG. 8.

FIG. 10 is a view similar to FIG. 2 but showing another embodiment of a discharge member subjected to reduced airflow and relatively low static pressure.

FIG. 11 is a cross-sectional view taken along line 11-11 of FIG. 10.

FIG. 12 is a view similar to FIG. 4 but showing the embodiment of FIGS. 2 and 3 with the discharge member being subjected to higher airflow and higher static pressure.

FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 12.

FIG. 14 is a view similar to FIG. 6 but showing another embodiment of a discharge member subjected to reduced airflow and relatively low static pressure.

FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 14.

FIG. 16 is a view similar to FIG. 8 but showing the embodiment of FIGS. 14 and 15 with the discharge member being subjected to higher airflow and higher static pressure.

FIG. 17 is a cross-sectional view taken along line 17-17 of FIG. 16.

DETAILED DESCRIPTION

FIG. 1 shows a variable air volume system 10 (VAV system) that comprises a tubular air duct 12 with a pliable wall 14 made of fabric such as polyester, vinyl, canvas, or some other type of pliable material. Duct 12 can be of any tubular cross-sectional shape including, but not limited to, round, semicircular, quarter-round, square, rectangular, triangular, etc. A variable speed blower 16, or some other type of pressurized air supply, forces air 18 through duct 12 at a variable flow rate for satisfying the heating, ventilating or air conditioning needs of a building. The static pressure of the air inflates duct 12 to its full-body shape. To release the air from within duct 12 and into various rooms or other areas of the building, a plurality of discharge members 20 are disposed on the pliable wall of duct 12.

Referring further to FIGS. 2-5, to minimize deflation and sagging of duct 12 when the flow rate of air 18 and/or the static pressure within duct 12 is relatively low, in some cases each discharge member 20 has a variable discharge opening 22 whose degree of opening decreases in response to a decrease in the static pressure or a decrease in the flow rate within duct 12. Thus, as the flow rate decreases to meet the building's demand, the static pressure within duct 12 will also decrease but not as much as it would if the open area of discharge members 20 were constant.

At low airflow rates, as shown in FIGS. 2 and 3, discharge opening 22 is relatively small to help maintain the static pressure within duct 12 at a certain threshold pressure that keeps duct 12 generally inflated. Conversely, at higher flow rates, as shown in FIGS. 4 and 5, discharge opening 22 is noticeably larger to enable duct 12 to deliver the desired airflow volume to the building.

Providing a discharge member with a pressure or volume responsive discharge opening can be achieved in various ways. Discharge member 20, for example, may comprise a crossed slit in the pliable wall of duct 12 to create the X-shaped discharge opening 22 of FIGS. 2 and 4. Depending on the resilience of the pliable wall's material, discharge member 20 may include a resilient stiffening structure 24, which may be an applied coating or a physical part that is sewn, bonded, or otherwise attached to wall 14. Resilient stiffening structure 24 may have an X-shaped opening that corresponds to that of opening 22. The end result could be a discharge member with one or more appropriately resilient flexible flaps 26 that tend to close discharge opening 22 in response to a decrease in the static pressure or airflow rate within duct 12. That is, the opening 22 is biased to the more closed position of FIG. 2 as opposed to the more open position of FIG. 4. This functionality helps maintain duct 12 in an inflated condition—even for reduced static pressure or airflow as may be provided for, by example, a VAV system.

In an alternate embodiment, shown in FIGS. 6-9, a pressure or volume responsive discharge member 28 redirects the air leaving duct 12 in response to the static pressure or airflow rate in the duct. In cases where less airflow is needed for heating than for cooling, discharge member 28 can direct reduced volume, warmer air downward, as shown in FIGS. 6 and 7, and can direct higher volume, cooler air upward, as shown in FIGS. 8 and 9.

To achieve this, discharge member 28 may include a relatively rigid vent plate 30 with a baffle 32 that protrudes through a cutout 34 in pliable wall 14. Cutout 34 creates beneath it a resiliently flexible flap 36, which is an integral extension of wall 14. The term, “integral extension,” refers to flap 36 and pliable wall 14 being of the same unitary material. Vent plate 30 can be attached to wall 14 in any suitable manner including, but not limited to, bonding, sewing, etc.

Upon reducing the static air pressure or airflow rate in duct 12, the natural resiliency of flap 36 tends to move it inward or to the right as viewed looking into FIGS. 7 and 9. Conversely, increasing the air pressure or flow rate in duct 12 moves flap 36 outward against its inward bias. Thus, at reduced airflow rates where the static pressure is low, flap 36 moves to the position of FIG. 7. This provides a discharge opening 38 between flap 36 and baffle 32 such that discharge member 28 directs the air in a more downward direction. In FIG. 9, however, air at higher static pressures and flow rates moves flap 36 outward so that discharge opening 38 between flap 36 and baffle 32 discharges the air in a more upward direction.

In another embodiment, shown in FIGS. 10-13, a discharge member 40 is an insert that overlays an opening 42 in a duct 12′ similar to duct 12. The operation of discharge member 40 is similar to that of discharge member 20, with FIGS. 10, 11, 12 and 13 corresponding to FIGS. 2, 3, 4 and 5, respectively. Discharge member 40 can be attached to duct 12 or 12′ in any number of ways, including, but not limited to, sewing, bonding, etc. Discharge member 40, in this example, includes an X-shaped discharge opening 44 that creates four resilient flaps 46. Due to the normal unstressed shape of member 40, flaps 46 tend to close discharge opening 44 in response to a decrease in the static pressure or airflow rate within duct 12′. Thus, as the airflow rate decreases within duct 12′, the closing of discharge opening 44 causes a backpressure that helps maintain the static pressure within duct 12′ at a threshold level that is sufficient for keeping duct 12′ generally inflated. Alternatively, in response to a reduction in static pressure within duct 12′, the closing off of discharge opening 44 reduces the airflow rate out of duct 12′ thus helping to maintain an adequate static pressure within duct 12′ to keep duct 12′ generally inflated. This same operating principle is common among the embodiments disclosed herein.

In another embodiment, shown in FIGS. 14-17, a discharge member 48 can be a generally rectangular insert that overlays an opening 50 in a duct 12″ similar to ducts 12 and 12′. The operation of discharge member 48 is similar to that of discharge member 28, with FIGS. 14, 15, 16 and 17 corresponding to FIGS. 6, 7, 8 and 9 respectfully. Discharge member 48 can be attached to ducts 12, 12′, or 12″ in any number of ways, including, but not limited to, sewing, bonding, etc.

Discharge member 48, in this example, includes an H-shaped discharge opening 52 that creates two generally rectangular resilient flaps 54 and 56, with flap 54 being stiffer than flap 56 due to the relative size, shape and or material composition of the two flaps. In the normal unstressed shape of member 48, flaps 54 and 56 tend to close discharge opening 52 in response to a decrease in the static pressure or airflow rate within duct 12″. Thus, when the static pressure or airflow rate within duct 12″ is relatively low, flaps 54 and 56 might only deflect to their positions of FIGS. 14 and 15, whereby the flaps direct the discharge air in a more downward direction.

When the static pressure or airflow rate increases, however, flaps 54 and 56 deflect farther out to the positions shown in FIGS. 16 and 17. Since flap 56 is more flexible than flap 54, flap 56 deflects more than flap 54 so that the flaps can now direct the discharge air in a more upward direction.

In cases where less airflow is needed for heating than for cooling, discharge member 48 can direct reduced volume, warmer air downward, as shown in FIGS. 14 and 15, and can direct higher volume, cooler air upward, as shown in FIGS. 16 and 17.

Although the invention is described with reference to a preferred embodiment, it should be appreciated by those of ordinary skill in the art that various modifications are well within the scope of the invention. VAV system 10, for example, is just one example of an air-handling system, and the subject invention can be applied to many other types of air-handling systems. Therefore, the scope of the invention is to be determined by reference to the following claims: 

1. An air-handling system for conveying air at a pressure, comprising: an air duct having a pliable wall; and a discharge member disposed on the pliable wall, wherein the discharge member defines a variable discharge opening having a degree of opening that varies with the pressure of the air within the air duct.
 2. The air-handling system of claim 1, wherein the degree of opening decreases with a decrease in the pressure of the air within the air duct.
 3. The air-handling system of claim 1, wherein the discharge member has at least a larger degree of opening and a smaller degree of opening and is biased toward the smaller degree of opening.
 4. The air-handling system of claim 1, wherein the discharge member includes a resiliently flexible flap that moves in response to a change in the pressure of the air within the air duct.
 5. The air-handling system of claim 1, wherein a portion of the discharge member is an integral extension of the pliable wall.
 6. The air-handling system of claim 1, wherein the discharge member releases the air in a direction that varies in response to a change in the pressure of the air within the air duct.
 7. The air-handling system of claim 1, wherein the discharge member releases the air in a more upward direction when the pressure of the air in the air duct increases.
 8. The air-handling system of claim 1, further comprising a variable speed blower in fluid communication with the air duct, whereby the variable speed blower can vary the pressure of the air in the air duct.
 9. An air-handling system for conveying air at a pressure, comprising: an air duct having a pliable wall; a variable speed blower in fluid communication with the air duct, wherein the variable speed blower can vary the pressure of the air in the air duct; and a discharge member disposed on the pliable wall, wherein the discharge member defines a variable discharge opening having a degree of opening that varies in response to the pressure of the air within the air duct.
 10. The air-handling system of claim 9, wherein the degree of opening decreases with a decrease in the pressure of the air within the air duct.
 11. The air-handling system of claim 9, wherein the discharge member has at least a larger degree of opening and a smaller degree of opening and is biased toward the smaller degree of opening.
 12. The air-handling system of claim 9, wherein the discharge member includes a resiliently flexible flap that moves in response to a change in the pressure of the air within the air duct.
 13. The air-handling system of claim 9, wherein a portion of the discharge member is an integral extension of the pliable wall.
 14. The air-handling system of claim 9, wherein the discharge member releases the air in a direction that varies in response to a change in the pressure of the air within the air duct.
 15. The air-handling system of claim 9, wherein the discharge member releases the air in a more upward direction when the pressure of the air in the air duct increases.
 16. A method for conveying air through an air duct, wherein the air is conveyed at a static pressure that can vary, the method comprising: forcing the air through the air duct; releasing the air from within the air duct through a discharge opening of the air duct; decreasing the static pressure of the air within the air duct; and altering the discharge opening in response to decreasing the static pressure of the air.
 17. The method of claim 16, wherein the step of altering the discharge opening involves restricting the discharge opening.
 18. The method of claim 16, wherein the step of altering the discharge opening involves redirecting the air through the discharge opening.
 19. The method of claim 16, wherein the step of altering the discharge opening involves deflecting a resiliently flexible flap.
 20. The method of claim 16, wherein the step of altering the discharge opening involves biasing the opening toward a smaller degree of opening.
 21. An air-handling system for conveying air at an airflow rate that varies, comprising: an air duct having a pliable wall; and a discharge member disposed on the pliable wall, wherein the discharge member defines a variable discharge opening having a degree of opening that varies with the airflow rate within the air duct.
 22. The air-handling system of claim 21, wherein the degree of opening decreases with a decrease in the airflow rate.
 23. The air-handling system of claim 21, wherein the discharge member has at least a larger degree of opening and a smaller degree of opening and is biased toward the smaller degree of opening.
 24. The air-handling system of claim 21, wherein the discharge member includes a resiliently flexible flap that moves in response to a change in the airflow rate.
 25. The air-handling system of claim 21, wherein the discharge member releases the air in a direction that varies in response to a change in the airflow rate.
 26. The air-handling system of claim 21, wherein the discharge member releases the air in a more upward direction when the airflow rate increases.
 27. The air-handling system of claim 21, further comprising a variable speed blower in fluid communication with the air duct, whereby the variable speed blower can vary the airflow rate.
 28. A method for maintaining the static pressure of air within an inflatable air duct, wherein the inflatable air duct conveys the air at an airflow rate that varies and releases the air through a discharge opening in the inflatable air duct, wherein the discharge opening is of a size that can vary, the method comprising: reducing the airflow rate through the inflatable air duct; and reducing the size of the discharge opening to maintain the static pressure above a certain threshold, thereby maintaining the inflatable air duct in an inflated state.
 29. The method of claim 28, wherein the step of reducing the size of the discharge opening is done automatically in response to the airflow rate being reduced. 